1. Field of the Invention
The present invention is related to a radiation imaging apparatus. More specifically, the present invention is related to a radiation imaging apparatus that urges a device to be employed in radiation images, to assist manual movement of the device.
2. Description of the Related Art
Conventionally, it is uncommon for small scale medical facilities, such as physicians in private practice and clinics, to install radiation imaging apparatuses dedicated to imaging specific portions of subjects. These medical facilities generally employ a single radiation imaging apparatus to perform radiation imaging of various body parts as necessary. For example, radiation imaging systems, in which an upright imaging table and a supine imaging table are installed in a single imaging room, a radiation source is supported by a ceiling runner suspension device or the like, and the irradiation direction of radiation is adjusted to be toward the upright imaging table and the supine imaging table by moving or changing the orientation of the radiation source, are known (refer to Japanese Unexamined Patent Publication Nos. 2009-005909 and 2007-244569).
There is also a known radiation imaging apparatus of the type described above, in which an operating handle is integrally formed with a device such as a radiation source, and when external forces are applied to the operating handle, the device is urged in the directions of the external forces to assist manual movement (hereinafter, this assistance will also be referred to as “power assistance”) of the device (refer to Japanese Unexamined Patent Publication No. 2000-316838).
In addition, there is a known apparatus that performs control of such power assistance such that a dead zone is provided (refer to Japanese Unexamined Patent Publication No. 2001-106082). For example, the external forces which are applied to the operating handle are measured, and the device is urged only when the measured external forces are greater than a predetermined value. By exerting control such that the dead zone is provided, unnecessary movement of the device due to inadvertent light contact with the operating handle or slight externally applied vibrations can be prevented.
Further, there is a known radiation imaging apparatus that executes the movement assistance by subtracting the weight of the operating handle itself from the external forces applied thereto, to more accurately perform control of the power assistance (refer to Japanese Unexamined Patent Publication No. 2000-316838). The control of the power assistance in this apparatus corrects the urging force used for power assistance, employing the inclination angle and the weight of the operating handle which is integrally formed with the device to be assisted in movement, which are stored in advance, to improve the operability when users move the device.
There are cases in which the settings for dead zones with respect to control of power assistance shift over time, due to changes in environment, and the like. That is, there are cases in which a dead zone range, which is initially set such that the power assistance urging force is generated when external forces exceeding 500 gf is applied onto an operating portion such as an operating handle from either the right or the left, shifts such that the power assistance urging force is generated when an external force applied from the left exceeds 700 gf and when an external force applied from the right exceeds 300 gf, for example. In cases that this type of shifting of dead zones occur, users sense the change in operability when moving the device with which the operating portion is integrally formed.
Further, if the shifting in the dead zone becomes great, there is a possibility that the power assistance urging force will be generated even when external force is not being applied to the operating section, resulting in the device to which the operating portion is mounted from moving in an uncontrolled manner.
In order to correct shifts in dead zones, it is necessary to interrupt radiation imaging to perform correction.
For this reason, there is demand to enable correction of shifts in dead zones with respect to control of power assistance without interrupting radiation imaging.